starting issue

i have a D reg gti with a dx engine in the car and for some reason it will not start im getting the fuel pump priming and getting fuel to the metering head but not to the injectors ive injected petrol in through the spark plug holes the car will briefly fire

i have been playing about with the air box today and moved the diafram plunger up and down and got fuel coming out so i did this while trying to start the car and it fired up and ran for 2 mins at idle no problem the coughed and spluttered and cut out but i cant get it to start again now any suggestions would be great guys thanks

Poor battery or poor wiring to the fuel pump.

wiring and battery are fine as i have replaced the battery with 1 off my mk2 gti and that runs fine does have a slight leak on pump though tbh but why would messing with the metering head get it to run ????

Slight leak on pump!!! That's the cause. The slight leak means there will be a drop in fuel pressure, which means the injectors won't open during hot starts. It will start from the fuel delivered by the 5th injector on cold starts, explaining the stuttering start it managed.

The metering head air flap probably isn't set correctly, and the mixture out too, but these are running issues rather than starting issues.

Or are you saying the car didn't start hot, then you fiddled with the metering head, then it started hot? If so then it will be a change in the mixture which did it. But then are you also saying it now doesn't start again?

the car was cold and would not start either hot or cold fuel is getting to the metering head and to the wur and 5th injector but the flap is just not allowing the fuel to go through but if you move it manually while trying to start the car it sometimes starts

if that makes sense

Fix the fuel leak and then retry, while it might be other issues too, the fact that there's a leak means the fuel pressure is lower. The K-Jet system relies on fuel pressure being correct.

Cold starts - check the 5th injector is firing - even with no fuel from the mechanical injectors, it would start and run for a few seconds if the 5th injector is doing its job properly.

Hot starts - correct operation of the metering head, and having proper system pressure, is much more critical - check the flap is centralised and sitting at the right level, that the WUR is working properly (will need a pressure gauge for this) and that the mixture is set properly (will need a gas analyser to properly do this).

thanks for that paul just need to find some 1 with a gauge now

what level should the flap be at so i can measure it it looks to me to be level with the base of the cone when i look at it

Cant remember, I think its either level; or .75mm below. Its in the Haynes manual though (in fact there's a good section on testing/setting up the K-Jet injection in there).

ok i have fixed the fuel leak and whippe3d out the 5th injector theher is power to the unit and fuel is getting to the 5th injector but iot is not firing any fuel through i have tried 2 injectors and still nothing i also pulled out injector no 1 and again no fuel remove the injector and still no fuel to the injector ????

the fuel pump is priming and fuel to the metering head and the wur  and the 5th injector but it delivers no fuel  im begining to get  really annoyed now with the car grrrrrr

update:- been messing about with the car a bit more today and when i manually operate the flap the car delivers fuel but does not start got a bit of back pressure into the air box , i have tried with and without air-filter all components that require power have power as i tested them with circuit tester the flap is central and it sits flush with the bottom of the bowl ( is this correct )

i have also tried another metering head from a 16 valve that i know is working but not sure if they do the same job but car wouldnt start any way

if 5th inj not spraying when engine is cold, you need to fix this.  there should be some black wires to the starter motor, make sure these are connected. also check the thermoswitch, its the big brown thing on the front coolant flange to head.  check the green/white wire pin has continuity to ground when the engine is stone cold.  note that if you're cranking car over for ages the thermoswitch will cut out fueling to the 5th injector, so only check 5th inj/thermoswitch pin when car is stone cold after standing for a long time/overnight.

if once all that working and it still wont start, replace the fuel filter. I had a blocked filter on my 16v and it had similar symptoms, car would get fuel to metering head but nothing out of the injectors

how do i check the continuity i know how to check for power at the plugs  which the 5th injector has and both black wires are on correctly at the starter  motor the fuel filter is a brand new cooper 1 on the metering head

car is always stone cold as it will not run

even if it hasnt started the 5th injector themoswitch can still cut out if you have been cranking it for ages like i said, as it gets a starter motor power feed.

to check for continuity you need a multimeter, set it so it shows a 1 and goes to 0 when the probes are touched, or the beep setting if it has one

put 1 end at the green/white wire at the thermoswitch, and the other at the green/white wire at the 5th injector. this wire should make the multimeter beep/go to 0.  Do the same test between the black wires at the starter motor and the black wire pin at the thermoswitch.

Next put 1 probe at the pin of the thermoswitch where the green/white wire goes, and the other at the battery -ve. this should also make the multimter beep/go to 0.

Next set the multimeter to measure voltage, and put the red probe to the black wire on the thermoswitch and the other to battery -ve. Get someone to crank the engine, and you should see 12v.

ok i have done the first test on the list this was fine and dropped down to zero

on the 2nd part of the test the thermo time switch is red and black so i assume this is what you meant when i tested this it does not drop down to zero ???

if you meant the black wire on the 5th injector this drops to zero  as above

part 3 checking green /white wire to batt neg the meter still reads 1 ??

part 4 when you check for voltage i get around 9 volts  any ideas on the above thanks

yeah sorry I meant check the black wire from starter to the 5th injector

part 3 I meant the actual pin on the thermoswitch, not the plug itself. you're checking the green/white wire pin passes current to ground when the switch is cold. if not it needs to be replaced.

9volts could be about right, after all there is quite a load on the starter motor while the engine is cranking?

a quick n dirty way to check the 5th inj is to take it out as you did above, and run the green/white wire from thermostwitch direct to ground.  then point it into a buckety and crank the engine, it should then spray fuel. if it does you can be pretty certain the problem is down to the thermoswitch, or the earthing path thru the block to ground.

if it still doesnt work maybe its the 9v you are seeing at the black wire isnt enough, to confirm jump the 5th inj pins direct to the battery whilst the fuel pump relay is bridged, if it sprays fuel then you know its ok.

oh and of course extreme care should be taken whilst messing with electrics and fuel!

update i have tried the continuity at the thermo time switch and it was at 113 so i earthed the plug straight to ground and it sprayed the fuel into a glass so i gues new thermo time switch required the flap in the air box is moving slightly and im getting a bit of back pressure into the air-box ??? i have taken out 1 of the injectors to check fuel delivery still nothing  though apart from the back pressure

I would say fixing the 5th injector will solve your problem. you can find these on most k-jet equipped cars, the MK2 16v is one of the newest modesl which still has the thermoswitch, its the same as a MK1 item and will fit straight on.

ok the thermo time switch has turned out to be faulty i have put a new 1 on today the car turns over and its firing every so often but will not take the final urge and start and when you think it will start im still getting back pressure through the air box and the engine stops turning briefley any ideas please thanks

I'd go back and double check the timing is spot on
take the rocker cover off and verify that when the crank and cam marks are lined up to TDC that the cam lobes on #1 look like this- |\  /|

also make sure the rotor arm is pointing at the notch oin the outer edge of the dizzy, and that spark plug lead #1 is fitted where the arm is pointing.  firing order is 1342 clockwise

firing order is ok from when we poured petrol into the bores the car ran and idled perfectly since then just the symptoms described